Radio interference eliminator



Oct. 1, '1935. w. K. FLEMING El AL RADIO INTERFERENCE ELIMINATORFi1ed.Nov. 23, 1931 Patented Get. 1, 1935 PATENT OFFICE.

RADIO INTERFERENCE ELIMINATOR Wilfred K. Fleming, Canton, and Rupert L.

Haskins, Boston, Mass.

Application November 23, 1931, Serial No. 576,652

2 Claims.

The present invention relates to means and methods of applyinginterference eliminating means to machines which cause interference withradio broadcast reception and other radio reception. The inventionrelates more in particular to the application to the elimination of suchinterference as caused by motors or gencraters which may have brushes orwhich may have contact making or breaking devices.

In such machines interference may be very objectionable as it maycontinue incessantly for some time. The invention described in thepresent application shows the application of ,the principle hereinvolved to a number of modifications in particular to a dentistdrilling motor and to an ordinary hand drill. One of the chiefdiiilcultles in applying interference eliminating means to such machinesis that there is little space in which such means can be placed and ifthe means are not placed near the machine, their useful effect might belost.

In the present invention the means are placed within the motor frame orin such close proximity to it that the leads are only a few inches long.The invention will be more clearly understood from an examination of thedrawing in connection with the description showing various embodimentsof the invention. In the drawing, Figure 1 shows a view of a dentaldrill motor with the coveh removed; Figure 2 shows the unit foreliminating interference; and Figure 3 illustrates the circuit.

In Figure 1 which represents a motor of the usual construction, there isprovided a frame which carries the coils 2, 3, etc.. for energizing themagnetic poles and the bearings l and I in which the rotor element i ofthe motor rotates.

The bearing i sets in a supporting collar I, forming a part of theframe. It is over this collar on the opposite end of the motor from thebrush end that the interference elemination unit 8 is placed. The unitcomprises'a flat piece 9 of metal or other suitable material which has ahole ll therein in which the hearing I fits. The

metallic plate 1 covers the surface of the collar 1 and is bent downwardon both sides thereof into curved supporting elements II and I2, whichmay be called condenser supporting clips. It will be noted from Figure 1that one supporting 50 clip or arm is at an angle with the other, namelythat they are not parallel and that the connecting lead It comes outupward from one end and the other upward from the other end. Thistogether with the little tabs 16 and I! at both ends of the condenserclips II and I2 help to keep the condensers l8 and i9 firmly in place.The condensers i8 and I9 snap or are pressed 5 in the holding elementsin any suitable or secure manner. The lead H as shown in Figure 1connects to one brush element 20, while the other lead l3 connects tothe other brush element 2| not shown in Figure 1. ,10

The element supporting the condensers I8 and I9 is somewhat the shape ofa saddle and is in fact saddled over the bearing 5 and collar 1. Itremains in place and practically without any support, but I prefer tohave the case 22 16 shown in fragment in section in Figure 1 fit snuglyover it and to have a nut 23 threading on the bearing 5 for furthersupport.

In Figure 3 is shown diagrammatically the circuit used in Figure l. Thecondensers l8 and 20 I9 are connected in series across the rotor by theleads I3 and H. In place of connecting across the rotor the lead i4 maybe connected to have the rotor and field 24 in series as shown by thedotted line 25 in Figure 3. The center 25 tap 26 between condensers IIand I8 is connected to the frame of the motor so that the frame itselfis at the mid-potential at all times. This may be accomplished asindicated in Figure 1 by connecting the condenser terminals 30 otherthan it and II together and grounding them to the saddle support I.

Having now described our invention, claim:

1. In combination with a drill motor having a 35 frame and a bearingsupported in said frame,

a saddle means adapted to fit over the bearing support and provided withcarrier elements extending inwardly of said frame, electricalinterference eliminating elements supported in said carrier elements,and means connecting said elements with the motor elements.

2. In combination with a drill motor having a frame and a bearingsupported in said frame, a saddle means adapted to fit over the bearingsupport and bent to form curved supporting elements positioned withinthe frame, condensers supported within said supporting elements andhaving connections connecting to the brushes of said motor.

wnmap K. name. m

RUPERT L. HASKINS.

